1. Field of the Invention
This invention relates to an automotive passenger restraint and protection apparatus for automotive vehicles such as automobiles, which uses an electric retractor for retracting and protracting a seatbelt for protection of an occupant (driver or passenger).
2. Prior Art
An automotive passenger restraint and protection apparatus is conventionally known, which has an electric retractor which protracts and retracts a seatbelt. The electric retractor has driving means formed, e.g. of an electric motor (hereinafter referred to as "motor" or "DC motor") for driving the electric retractor.
In the conventional automotive passenger restraint and protection apparatus of this type, fault diagnosis of the apparatus is carried out by pulling out or releasing a seatbelt by the occupant to ascertain whether the seatbelt can be actually protracted or retracted.
The above manner of fault diagnosis is unable to accurately detect faults in a DC motor for driving the electric retractor and its peripheral parts.
There have been proposed many other fault diagnosis methods for automotive passenger restraint and protection apparatuses.
One of these conventional methods is a method of detecting temperature in the vicinity of the motor by a temperature sensor or detecting current flowing to the motor by a current detecting circuit, and determining by an MPU (Micro Processing Unit) of the apparatus that there is is a fault in the apparatus when the detected temperature value or current value continuously exceeds a predetermined value over a predetermined time period. Upon determination that there is a fault in the apparatus, the MPU causes the motor to be stopped to prevent firing of the motor.
According to the above fault diagnosis method, however, if an abnormality occurs in a power transmission mechanism which transmits a driving force from the motor to a reel shaft which has the seatbelt wound thereon such that the power transmission cannot transmit the driving force and accordingly the motor runs idle, the temperature in the vicinity of the motor rises and the current flowing to the motor increases but not to such a degree that the MPU can determine that there is a fault or abnormality. Consequently, such a kind of abnormality cannot be detected by the conventional fault diagnosis method.
Further, if no countermeasure is taken to eliminate such an abnormality of the power transmission mechanism, the motor may have a shortened effective life.
On the other hand, if the motor for driving the electric retractor is continuously operated for a long time, the temperature of the motor rises and can exceed the withstand temperature so that the motor can become faulty.
The conventional automotive passenger restraint and protection apparatus, however, is not provided with a function of preventing such a kind of fault.
The conventional automotive passenger restraint and protection apparatuses include a type which has a function of carrying out a seatbelt slackening operation for giving a predetermined amount of looseness to the seatbelt if seatbelt attaching detecting means detects that the seatbelt has shifted from a state disconnected from the occupant to a state attached to the occupant, and carrying out a seatbelt storing operation for storing the seatbelt into a retracted position if the seatbelt attaching detecting means detects that the seatbelt has shifted from the attached state to the disconnected state.
Further, the conventional automotive passenger restraint and protection apparatuses include a type which has a function of carrying out a seatbelt slackening operation of retracting the seatbelt to a retraction limit position (hereinafter merely referred to as "limit" unless otherwise specified) if the seatbelt is protracted by the occupant in attaching the seatbelt to his body, and then protracting the seatbelt so as to give a predetermined amount of looseness to the seatbelt.
If, however, the seatbelt attaching detecting means becomes faulty such that it always determines that the seatbelt is disconnected from the occupant even when the seatbelt is attached to the occupant, the seatbelt slackening operation cannot be performed even when the seatbelt has been attached to the occupant, whereby a predetermined amount of looseness cannot be given to the seatbelt, failing to providing a comfortable seatbelt wearing feeling for the occupant. Further, even if the seatbelt has shifted to the disconnected state from the attached state with the seatbelt attaching detecting means being faulty, the seatbelt storing operation cannot be performed, so that the seatbelt is held in the disconnected or protracted state.
Conversely, if the seatbelt attaching detecting means becomes faulty such that it always determines that the seatbelt is attached to the occupant even when the seatbelt is disconnected from the occupant, the seatbelt slackening operation can be carried out while the seatbelt is in the stored state, failing to keep the seatbelt in a proper stored state. Further, in this state, if the seatbelt is attached to the occupant' body, a determination is made that the seatbelt has been protracted from a state attached to the occupant, so that the seatbelt slackening operation is carried out. However, if then the seatbelt is disconnected from the occupant, a determination is made that the seatbelt is attached to the occupant, so that the seatbelt storing operation cannot be performed, whereby the seatbelt is held in the protracted state.
Moreover, in the above type of automotive passenger restraint and protection apparatus, the seatbelt is always given a fixed amount of looseness irrespective of whether there is a fear of collision of the automotive vehicle. Therefore, the above function is not perfect to properly protect the occupant.
Further, in the conventional automotive passenger restraint and protection apparatus, the power consumption of the MPU is not contemplated. As a result, for example, the MPU operates so as to exhibit its full function even in the case where the full function of the MPU need not be exhibited.
On the other hand, an automotive passenger restraint and protection apparatus is conventionally known, which is provided with driving/traveling state detecting means which detects a collision danger state and a collision unavoidable state of the automotive vehicle, and a dozing state of the driver.
According to this type of automotive passenger restraint and protection apparatus, if the driving/traveling state detecting means detects the collision danger state of the automotive vehicle or the dozing state of the driver, protraction and retraction of the seatbelt are alternately carried out at irregular time intervals so as to alert the occupant or driver to the danger. Further, if the collision unavoidable state of the automotive vehicle is detected, the seatbelt is retracted with a predetermined magnitude of retracting force so as to properly protect the occupant upon a collision of the automotive vehicle.
In the conventional automotive passenger restraint and protection apparatus, however, once the ignition switch of the automotive vehicle is turned on, electric power is supplied from the power supply all the time thereafter, so that the electric power is consumed even when the driving/traveling state detecting means need not be operated.
Further, the electric retractor is constructed such that once disconnection of the seatbelt from the occupant is detected, it retracts the seatbelt into its fully retracted position.
Therefore, if the occupant once releases a tongue of the seatbelt from a buckle secured to the seat into a disconnected state and immediately then attaches the tongue of the seat to the buckle, he has to manually protract the seatbelt against the retracting force of the electric retractor. Thus, a large force is required for protracting the seatbelt, and therefore a weak occupant who has degraded physical ability such as an advanced-age occupant takes long to mount the seatbelt onto his body.
Further, an automotive passenger restraint and protection apparatus has been proposed, e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 9-175327, which includes an electric retractor, and collision danger predicting means, wherein the electric retractor operates in response to a signal indicative of collision danger from the collision danger predicting means, to cause vibration by alternately applying and releasing pressure to and from the occupant through the seatbelt. This vibration is continued until a signal indicative of a collision being unavoidable is received from the collision danger predicting means or the signal indicative of collision danger ceases to be received.
The proposed automotive passenger restraint and protection apparatus are, however, required to be still improved in the following points. That is, the collision danger predicting means merely predicts or foresees a future phenomenon but cannot perfectly predict a future phenomenon. Therefore, according to the proposed construction that stops vibration by alternate application and release of pressure upon stopping of receipt of the collision danger signal, the collision danger signal is not received even when there is still a possibility that the vehicle encounters a collision, so that the vibration is stopped. Thus, sufficient warning cannot be given to the occupant.
Further, in the conventional automotive passenger restraint and protection apparatus, in the case where when the seatbelt is in a state disconnected from the occupant, when the seat is protracted by the occupant, the time period after the protraction of the seatbelt by the occupant is stopped and before retraction of the seat is started by the electric retractor is almost constant irrespective of the speed of the protraction of the seatbelt by the occupant. More specifically, the occupant with the seatbelt not attached to his body protracts the seatbelt in order to mount the seatbelt onto his body, and thereafter stops protracting the seatbelt since he cannot easily soon engage the tongue of the seatbelt with the buckle and hence takes time to mount the seatbelt onto his body. The time period after the stoppage of protraction of the seatbelt by the occupant and before retraction of the seatbelt by the electric retractor is started is set to a predetermined fixed time period which corresponds to the expected time that the occupant should take by trying to engage the seatbelt with the buckle.
However, if the occupant protracts the seatbelt without the intention of mounting the seatbelt onto his body and then gets off the automotive vehicle and closes the door, retraction of the seatbelt by the electric retractor is not carried out over the set predetermined time period. As a result, the protracted seatbelt can be caught in the door when the occupant closes the door. On the other hand, in the case where the occupant takes longer time than expected to mount the seatbelt onto his body, retraction of the seatbelt by the electric retractor can start before the occupant completes the mounting. Then, the occupant takes long to mount the seatbelt onto his body due to the retracting force of the electric retractor.
The time period after the seatbelt is protracted by the occupant and before he closes the door after getting off the automotive vehicle varies depending upon the occupant's physical ability. Generally speaking, in the case of an occupant having a high physical ability, the time the occupant takes to get off the vehicle is short and the time period after the occupant protracts and before he closes the door is short, whereas in the case of an occupant having a low physical ability, the time the occupant takes to get off the vehicle is long and the time period after the occupant protracts and before he closes the door is long. Further, generally speaking, the seatbelt protracting speed of an occupant of a high physical ability is high, whereas that of an occupant of a low physical ability is low. Accordingly, generally, the time period after stoppage of protraction of the seatbelt by the occupant and before completion of mounting of the seatbelt onto his body is relatively short in the case of an occupant of a high physical ability, and relatively long in the case of an occupant of a low physical ability.
In the conventional automotive passenger restraint and protection apparatus, however, the time period after the stoppage of protraction of the seatbelt by the occupant and before the start of retraction of the seat by the electric retractor is set to an almost constant value irrespective of the physical ability of the occupant. Therefore, if the set time period is a relatively long time period corresponding to an occupant of a low physical ability, when an occupant of a high physical ability gets off the vehicle and closes the door in a relatively short time, the seatbelt can be caught in the door, while if the set time period is a relatively short time period corresponding to an occupant of a high physical ability, when an occupant of a low physical ability mounts the seatbelt onto his body, the seatbelt starts to be retracted by the electric retractor before he finishes mounting the seatbelt onto his body, thus impeding the occupant's mounting motion.
Further, in the conventional automotive passenger restraint and protection apparatus, supply voltage to the electric retractor is supplied from a battery provided in the automotive vehicle all the time, as known from Japanese Laid-Open Utility Model publication (Kokai) No. 61-134464. Further, in the apparatus according to this publication, the seatbelt is not retracted after disconnection of the seatbelt from the occupant.
According to this conventional automotive passenger restraint and protection apparatus, however, since the supply voltage to the electric retractor is supplied from the batter all the time, the battery is consumed even when the supply voltage need not be supplied to the electric retractor, resulting in early deterioration of the battery. Further, since the seatbelt is not retracted after disconnection of the seatbelt from the occupant, there is a possibility that the tongue of the seatbelt can be caught in the door.